Researches have discovered that a species of grasshopper has the largest testicles of any living creature, relative to body weight.

In a comparison of 21 species of bushcricket published in Biology Letters, scientists found that the tuberous bushcricket (Platycleis affinis) have testes making up 13.8% of their bodyweight, AFP reports.

However, the researchers also discovered that the grasshoppers did not produce more sperm per ejaculate than others.

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Karim Vahed, a behavioural ecologist at the University of Derby, said: "We couldn't believe the size of these organs. They seemed to fill the entire abdomen.

"Extra large testes in bushcrickets allow males to transfer relatively small ejaculates to a greater number of females. Males don't put all their eggs - or rather sperm - in one basket."

James Gilbert, a researcher at Cambridge University, added: "Traditionally it has been pretty safe to assume that when females are promiscuous, males use monstrously-sized testicles to deliver huge amounts of sperm to swamp the competition.

"Our study shows that we have to rethink this assumption. It looks as though the testes may be that big simply to allow males to mate repeatedly without their sperm reserves being exhausted."